Articulated machines are used in a wide variety of heavy duty applications. In a typical design, such as any one of various wheel loaders used, for example, in construction, mining, forestry, and waste handling, a set of front wheels are coupled with a front frame unit and a set of back wheels are coupled to a back frame unit. The frame units articulate about an articulation axis at one or more articulation joints. An articulation steering system will typically include hydraulic actuators which urge the frame units to rotate about the articulation axis relative to one another. It is common for articulated machines to have very dynamic operation, moving forward and moving back repeatedly, and steering to change the articulation angle between the frame units many times over the course of a work cycle. Due to such general patterns of machine movement, and the otherwise rugged conditions involved in moving material and traveling over rough terrain, the hardware used in articulation joints needs to be fairly robust.
It is therefore common for the components of articulation joints to be relatively large and sturdy, capable of withstanding and transmitting loads in the many thousands of pounds, and rotating back and forth thousands of times over the course of a service life. Lubrication and lubricant sealing systems are also commonly provided in or in association with articulation joints to lubricate various of the components, and extend their service life. As a result of the foregoing and other factors, articulation joints for heavy machinery tend to be significantly more complex, expensive, and precisely engineered than simple hitch constructions.
One articulation joint design is known from U.S. Pat. No. 5,366,299 to Hughes, entitled Articulation Vehicle And Hinge Assembly. Hughes proposes a hinge assembly for front and rear frame portions of an articulated vehicle, where rotatable protruding trunnions join the front and rear frame portions at each one of a pair of vertically aligned hinges. In the trunnion, a spacer ring is placed against one of two bearing cones positioned upon a shoulder of a pin, and is biased against the one of the bearings via an end cap secured to the pin. A plurality of bolts are apparently used to secure the subject end cap to the pin, and apply a preload to the bearing via the spacer. A shim pack is placed between the end cap and the end of the pin to control the preload.